Force multiplying type archery bow

ABSTRACT

An archery bow includes a handle having resilient limbs secured thereto and extending outwardly therefrom. A pair of eccentric sheaves are revolvably mounted on the handle and a pair of pulleys are revolvably mounted on the ends of the limbs. A bowstring has its ends anchored to the handle and is trained about the eccentric sheaves and pulleys to define a nocking stretch. When the bowstring is drawn, the eccentric sheaves produce an overcenter action so that the force beyond this point is less than the force required at an intermediate draw position. A pair of concentric sheaves are each connected to one of the eccentric sheaves, and an endless crossed cable is trained about these concentric sheaves to thereby cause the eccentric sheaves to rotate in unison during movement of the nocking stretch between drawn and rest positions.

United States Patent [191 Hofmeister [4 1 Dec. 17,1974

[ FORCE MULTIPLYING TYPE ARCHERY BOW [75] Inventor:

[73] Assignee: Herters, lnc., Waseca, Minn.

[22] Filed: Mar. 14, 1974 [211 App]. No.: 451,212

Russell l-lofmeister, Waseca, Minn.

Primary Examiner-George J, Marlo Assislan! Examiner-William R. BrowneAttorney, Agent, or Firm-W1lliamson, Bains & Moore [57 1 ABSTRACT Anarchery bow includes a handle having resilient limbs secured thereto andextending outwardly therefrom. A pair of eccentric sheaves arerevolvably mounted on the handle and a pair of pulleys are revolvablymounted on the ends of the limbs. A bowstring has its ends anchored tothe handle and is trained about the eccentric sheaves and pulleys todefine a nocking stretch. When the bowstring is drawn, the eccentricsheaves produce an overcenter action so that the force beyond this pointis less than the force required at an intermediate draw position. A pairof concentric sheaves are each connected to one of the eccentricsheaves, and an endless crossed cable is trained about these concentricsheaves to thereby cause the eccentric sheaves to rotate in unisonduring movement of the nocking stretch between drawn and rest positions.

4 Claims, 8 Drawing Figures FORCEMULTIPLYING TYPE ARCHERY BOW SUMMARY OFTHE INVENTION This invention relates to an archery bow.

Certain archery bows have been developed to incorporate eccentricpulleys to produce an overcenter effect when the bowstring is drawn. Inthese bows, the bowstring is trained about the eccentric pulleys, whichare usually mounted on the tips of the limbs or closely adjacent thelimb tips. However, in archery bows of this construction, the eccentricpulleys may not rotate in unison if the eccentric pulleys are notsubjected to the same pulling force. Unequal pulling forces may beexerted on the eccentric pulleys when the nocking stretch is grippedoffcenter with respect to its longitudinal center point.

It is therefore a general object of this invention to provide .anarchery bow having a pair of eccentric sheaves revolvably mounted on thebow handle about which the bowstring is trained to produce anovercenside plates 13, the side plates being rigidly secured to thehandle member by suitable screws 14.

The archery bow also includes a pair of elongate flexible resilientlimbs 15, each having its inner end positioned between and pivotallysecured to a pair of side plates by a pivot 16. Each limb is providedwith a limb adjustment member 17, which in the embodiments shown,comprises a threaded bolt which extends through a slot in the limb baseand which is secured to the handle by means of a threaded insert.Manipulation of the limb adjustment member 17 for each limb, permitseach associated limb to be pivotally adjusted for tiller andpullweights.

It will be noted that the side plates 13 project rearwardly from thehandle member 11 and each pair of plates accommodates therebetween acompound sheave structure 18. Each compound sheave structure 18 includesan eccentric sheave l9 and a concentric sheave keyed to a sheave axle21, the latter being 20 journaled in openings in the side plates 13.Suitable reter effect when the bowstring is drawn. In the presentinvention, a pair of concentric sheaves are each connected to one of theeccentric sheaves for rotation therewith, and the crossed connectingcable is trained about the concentric sheaves to assure simultaneousrotation of the eccentric sheaves when the bowstring is drawn.

These and other objects and advantages of this invention will more fullyappear from the following description made in connection with theaccompanying drawings wherein like reference characters refer to thesame or similar parts throughout the several views.

FIGURES OF THE DRAWINGS FIG. 1 is a side elevational view of the novelarchery bow;

FIG. 2 is an enlarged, cross-sectional view taken approximately alongline 2-2 of FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a cross-sectional view taken approximately along line 3 -3 ofFIG. 2 and looking in the direction of thearrows;

FIG. 4 is a cross-sectional view taken approximately along line 44 ofFIG. 3 and looking in the direction of the arrows;

FIG. 5 is a cross-sectional view taken approximately along line 5-5 ofFIG. 2 and looking in the direction of the arrows;

FIG. 6 is a cross-sectional view taken approximately along line 6-6 ofFIG. 5 and looking in the direction of the arrows;

FIG. 7 is a diagrammatic elevational view illustrating a portion of thearchery bowstring and FIG. 8 is a diagrammatical elevational viewillustrating the connecting cable and the concentric sheaves of thearchery bow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring nowto the drawings, and more specifically to FIG. 1, it will be seen thatone embodiment of the novel archery bow, designated generally by thereference numeral 10 is there shown. The bow I0 includes an elongatehandle member 11 which is provided with a conventional arrow shelf 12.Each end portion of the handle member 11 is provided with a pair ofsimilar taining clips 22 secures the ends of the sheave axle in mountedrelation within the associated side plates 13. It will also be notedthat the eccentric sheave 19 of each compound sheave structure 18 isfixedly connected to the associated concentric sheave 20 by a pair ofbolts or screws 190. Thus each eccentric sheave and its associatedconcentric sheaves are adapted to rotate as a unit relative to theassociated side plates.

Referring now to FIGS. 2, 3 and 4, it will be seen that each eccentricsheave 19 has a pair of grooves 23 therein, each groove extendingthroughout the circumference of the eccentric sheave. It will be notedthat these grooves are disposed in substantially parallel planes, andeach is connected by a cable passage 25 which extends generallydiametrically through the eccentric sheave from one groove 23 thereininto the other groove therein. Referring now to FIGS. 2, 5 and 6, itwill be seen that the concentric sheave 20 also has a pair of grooves 25therein, each extending throughout the circumference of the sheave. Thegrooves 25 in the concentric sheave are also disposed in substantiallyparallel planes, and each is connected by a cable passage 26 whichextends substantially diametrically through the concentric sheave tointercommunicate one groove with the other.

Referring now to FIGS. 1 and 7, it will be seen that each of the limbs15 is provided with a generally U- shaped pulley bracket 27, fixedlymounted thereon adjacent the tip of the limb, each pulley bracketrevolvably mounting a pulley 28 by means of a pulley axle 29. Eachresilient limb 15 is also provided with a second pulley bracket 30fixedly mounted thereon and which has a conventional pulley 31 journaledthereon by means of an axle 32. It will be noted that each pulley 31 ismounted adjacent but is spaced from the associated pulley 28.

The archery bow also includes a bowstring assembly 33 which is comprisedof a pair of elongate similar anchor cables 34, each having one endthereof secured to an anchor 35. In this respect, it will be noted thateach anchor 35 actually comprises a transverse shaft which extendsbetween and which is journaled in the associated side plates 13.Although not shown in the drawing,

each anchor shaft may be adjusted by means of meshing gears (one ofwhich is a worm gear) to wind or unwind the anchored end of the anchorcable attached thereto. Each anchor cable extends upwardly from itsassociated anchor and is trained about the pulley 31 and is thereaftertrained about the grooves 23 in the eccentric sheave 19. in thisrespect, each anchor cable is positioned in one of the grooves 23 in aneccentric sheave l9, and the cable then extends through the cablepassage 24 to be positioned in the other groove of the eccentric sheave.Thereafter, the anchor cable is trained about the pulley 28 and issecured to a terminal 36 at its other end.

The bowstring assembly also includes a bowstring 37 which is secured atopposite ends. to the cable terminal 36. The bowstring 37 actuallyconstitutes the nocking stretch of the bowstring assembly and mayinclude a nocking point 38. It will be seen that when the bowstring ispulled from a rest position as illustrated in HO. 1, to a drawnposition, the anchoring cables will cause the eccentric sheaves torotate as the bowstring assembly is progressively tensioned or drawn.Thus the eccentric sheaves will pass through an overcenter positionwherein the maximum force required during drawing of the bowstringassembly occurs at an intermediate position. Since the maximum drawforce occurs at an intermediate position, less force is required to holdthe bowstring beyond the overcenter position of the eccentric sheavesand it is therefore easier for an archer to hold the bow in a shootingposition.

lt is also desirable to have the eccentric sheaves rotate in unison inorder to have the arrow subjected to a balanced uniform impelling force.In order to assure rotation of the eccentric sheaves in unison, anendless connecting cable 39 is trained about the concentric sheave ofthe compound sheave structures 18. In this respect, it will be notedthatthe connecting cable 39 is trained about one of the grooves in oneof the concentric sheaves and the connecting cable is then directedthrough the cable passage 26 and is positioned in the other groove ofthe concentric sheave. It will also be noted that the connecting cable59 is crossed, as best seen in FIGS. 1 and 8. It will be appreciatedthat the cable is first applied to the grooves and cable passages in theconcentric sheaves, and the ends of the cable are thereafter spliced.

During use of the bow, the bowstring will be drawn from the restposition to a drawn position and this movement of the bowstring assemblywill cause rotation of the eccentric sheaves 19. As pointed out above,when the eccentric sheaves are rotated through an overcenter position,the bowstring may be more easily held in a shooting position since themaximum drawing force occurs in an intermediate drawn position. It willbe noted that since each eccentric sheave is fixedly connected to itsassociated concentric sheave, movement of either eccentric sheave willimpart the same rotative movement to the other eccentric sheave. It isalso pointed outthat by directing each of the anchor cables through thecable passages of the eccentric sheaves, the bowstring assembly is, ineffect, connected to the eccentric sheaves. Similarly, by passing theconnecting cable through the cable passages in the concentric sheaves,the connecting cable is connected to the concentric sheaves. Therefore,a very positive rotative action is exerted on the compound sheavestructures 18 at all times. It is also pointed out that by mounting thecompound sheave structures 18 on the handles, the present bow avoids theuse of a plurality of stretches which extend completely between therespective tips of the limbs. Thus, my novel archery bow is capable ofobtaining the mechanical advantage (overcenter action) through the useof eccentric sheaves, but these eccentric sheaves are interrelated witheach other to assure rotation of the eccentric sheaves in unison.

From the foregoing description, it will be seen that l have provided anovel archery bow, which is not only of simple and inexpensiveconstruction, but one which functions in a more efficient manner thanthe heretofore known comparable archery bow.

What is claimed is:

1. An archery bow comprising:

an elongate handle member having spaced apart ends,

a pair of elongate resilient limbs connected to the ends of said handlemember and projecting outwardly therefrom, said limbs having freeterminal ends,

a bowstring support means mounted on said limbs adjacent the freeterminal ends thereof,

a pair of similar eccentric sheaves, each eccentric sheave of said pairof eccentric sheaves being revolvably mounted on said handle immediatelyadjacent each end thereof, a pair of concentric sheaves, each concentricsheave of said pair of concentric sheaves being fixedly connected to anassociated one of said eccentric sheaves and revolvable therewith,

a bowstring assembly having opposite free ends thereof connected withsaid handle and being trained about said spaced apart eccentric sheavesand about said bowstring support means and defining a nocking stretchbetween said bowstring support means, said nocking stretch being movablebe tween drawn and rest positions, said eccentric sheaves beingrevolvable. in response to movement of the nocking stretch between thedrawn and rest positions,

an elongate flexible, endless connecting cable trained about said spacedapart concentric sheaves to define a pair of stretches which cross eachother and cooperating with said concentric sheaves to cause saideccentric sheaves to rotate in unison in response to movement of thenocking stretch between drawn and rest position.

2. The archery bow as defined in claim 1 wherein each eccentric sheavehas a pair of circumferential grooves in the surface thereof, and apassage extending generally diametrically through each sheaveintercommunicating one groove in eccentric sheave with the other groovethereof.

3. The archery bow as defined in claim 1 wherein each concentric sheavehas a pair of circumferential grooves in the surface thereof, and apassage extending diametrically through each concentric sheaveintercommunicating one groove in an eccentric sheave with the othergroove thereof, said bowstring assembly being positioned in the groovesof each concentric sheave and extending through the passage therein.

4. The archery bow as defined in claim 1 wherein said bowstring supportmeans comprises at least one pair of pulleys, each pulley being mountedon one of said limbs adjacent the end thereof.

1. An archery bow comprising: an elongate handle member having spacedapart ends, a pair of elongate resilient limbs connected to the ends ofsaid handle member and projecting outwardly therefrom, said limbs havingfree terminAl ends, a bowstring support means mounted on said limbsadjacent the free terminal ends thereof, a pair of similar eccentricsheaves, each eccentric sheave of said pair of eccentric sheaves beingrevolvably mounted on said handle immediately adjacent each end thereof,a pair of concentric sheaves, each concentric sheave of said pair ofconcentric sheaves being fixedly connected to an associated one of saideccentric sheaves and revolvable therewith, a bowstring assembly havingopposite free ends thereof connected with said handle and being trainedabout said spaced apart eccentric sheaves and about said bowstringsupport means and defining a nocking stretch between said bowstringsupport means, said nocking stretch being movable between drawn and restpositions, said eccentric sheaves being revolvable in response tomovement of the nocking stretch between the drawn and rest positions, anelongate flexible, endless connecting cable trained about said spacedapart concentric sheaves to define a pair of stretches which cross eachother and cooperating with said concentric sheaves to cause saideccentric sheaves to rotate in unison in response to movement of thenocking stretch between drawn and rest position.
 2. The archery bow asdefined in claim 1 wherein each eccentric sheave has a pair ofcircumferential grooves in the surface thereof, and a passage extendinggenerally diametrically through each sheave intercommunicating onegroove in eccentric sheave with the other groove thereof.
 3. The archerybow as defined in claim 1 wherein each concentric sheave has a pair ofcircumferential grooves in the surface thereof, and a passage extendingdiametrically through each concentric sheave intercommunicating onegroove in an eccentric sheave with the other groove thereof, saidbowstring assembly being positioned in the grooves of each concentricsheave and extending through the passage therein.
 4. The archery bow asdefined in claim 1 wherein said bowstring support means comprises atleast one pair of pulleys, each pulley being mounted on one of saidlimbs adjacent the end thereof.